btl/uct: correctly set the completion status before using uct completions

According to UCT documentation the status field must be preset to UCS_OK before
the completion is used. My assumption here is that the field is not filled in in
all cases leaving the value as potentially garbage. This CL addresses the issue
but setting the status in the constructor for both RDMA completions and frags.
The status is then reset on completion callback.

Signed-off-by: Nathan Hjelm <[email protected]>

Author: hjelmn

opal/mca/btl/uct/btl_uct_frag.c

@@ -2,6 +2,7 @@
 /*
  * Copyright (c) 2018      Los Alamos National Security, LLC. All rights
  *                         reserved.
+ * Copyright (c) 2025      Google, LLC. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -26,7 +27,13 @@ static void mca_btl_uct_frag_completion_compat(uct_completion_t *uct_comp, ucs_s
 
 #if UCT_API >= ((1L<<UCT_MAJOR_BIT)|(10L << UCT_MINOR_BIT))
 static void mca_btl_uct_frag_completion(uct_completion_t *uct_comp) {
-    mca_btl_uct_frag_completion_compat(uct_comp, uct_comp->status);
+    ucs_status_t status = uct_comp->status;
+    /* reset the status now as the completion can not be accessed after calling
+     * mca_btl (may get returned) */
+    uct_comp->status = UCS_OK;
+
+    mca_btl_uct_frag_completion_compat(uct_comp, status);
+    /* do not access the completion struture here */
 }
 #else
 static void mca_btl_uct_frag_completion(uct_completion_t *uct_comp, ucs_status_t status) {
@@ -42,14 +49,11 @@ static void mca_btl_uct_base_frag_constructor(mca_btl_uct_base_frag_t *frag)
     memset((char *) frag + sizeof(frag->base), 0, sizeof(*frag) - sizeof(frag->base));
 
     OBJ_CONSTRUCT(&frag->comp, mca_btl_uct_uct_completion_t);
+    frag->comp.frag = frag;
 
     frag->base.des_segments = frag->segments;
     frag->base.des_segment_count = 1;
 
-    frag->comp.uct_comp.func = mca_btl_uct_frag_completion;
-    frag->comp.uct_comp.count = 1;
-    frag->comp.frag = frag;
-
     frag->segments[0].seg_addr.pval = frag->base.super.ptr;
     frag->uct_iov.buffer = frag->base.super.ptr;
     frag->uct_iov.stride = 0;

opal/mca/btl/uct/btl_uct_rdma.c

@@ -2,6 +2,7 @@
 /*
  * Copyright (c) 2014-2018 Los Alamos National Security, LLC. All rights
  *                         reserved.
+ * Copyright (c) 2025      Google, LLC. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -18,15 +19,21 @@ static void mca_btl_uct_uct_completion_compat(uct_completion_t *uct_comp, ucs_st
                                                   - offsetof(mca_btl_uct_uct_completion_t,
                                                              uct_comp));
 
-    BTL_VERBOSE(("network operation complete. status = %d", status));
+    BTL_VERBOSE(("network operation complete. frag = %p, status = %d", (void *) comp->frag, status));
 
     comp->status = status;
     opal_fifo_push(&comp->dev_context->completion_fifo, &comp->super.super);
 }
 
 #if UCT_API >= ((1L<<UCT_MAJOR_BIT)|(10L << UCT_MINOR_BIT))
 static void mca_btl_uct_uct_completion(uct_completion_t *uct_comp) {
-    mca_btl_uct_uct_completion_compat(uct_comp, uct_comp->status);
+    ucs_status_t status = uct_comp->status;
+    /* reset the status now as the completion can not be accessed after calling
+     * mca_btl_uct_uct_completion_compat (may get returned) */
+    uct_comp->status = UCS_OK;
+
+    mca_btl_uct_uct_completion_compat(uct_comp, status);
+    /* do not access the completion struture here */
 }
 #else
 static void mca_btl_uct_uct_completion(uct_completion_t *uct_comp, ucs_status_t status) {
@@ -38,6 +45,11 @@ static void mca_btl_uct_uct_completion_construct(mca_btl_uct_uct_completion_t *c
 {
     comp->frag = NULL;
     comp->uct_comp.func = mca_btl_uct_uct_completion;
+    comp.uct_comp.count = 1;
+
+#if UCT_API >= ((1L<<UCT_MAJOR_BIT)|(10L << UCT_MINOR_BIT))
+    comp->uct_comp->status = UCS_OK;
+#endif
 }
 
 OBJ_CLASS_INSTANCE(mca_btl_uct_uct_completion_t, opal_free_list_item_t,